1. Field of the Invention
This invention relates to a muffler device for an internal combustion engine, and more particularly, to a muffler having a porous partition wall arranged therein. 2. Description of the Background Art
Japanese Utility-Model Laid-Open No. Sho 56-83622 discloses a muffler device in which an inner side of the muffler is partitioned by a plurality of partition walls to form a plurality of expansion chambers in a lengthwise direction. Each of the expansion chambers communicates with a communicating pipe. At the same time, a porous partition wall is arranged near an outlet port of a feeding pipe communicating with the exhaust pipe.
In the above embodiment, when a certain distance is not maintained between an outlet of the feeding pipe and the porous partition wall, an undesirable influence may occur hindering the efficient flow of exhaust. Although the porous partition wall is arranged at a right angle with respect to an axial line of the feeding pipe, the outlet port of the feeding pipe cannot be arranged near the porous partition wall by an amount more than a specified distance. Therefore, the size of the muffler must be increased.
When the feeding pipe and the communicating pipe are overlapped with one another, the porous partition wall must be bent in order to be arranged between the feeding pipe and the communicating pipe. The result is that a shape of the porous partition wall may become complicated.
When a plurality of feeding pipes or communicating pipes are present near or passing through the porous partition wall, an extending position of each of the pipes on the porous partition wall must avoid formation of some small holes. Thus, as the number of feeding pipes or communicating pipes is increased, a range of small holes which can be formed at the porous partition wall is limited, and an opening area of the small holes is reduced.
However, if each of the aforesaid problems is to be resolved concurrently, the structure inside of the muffler may become complicated. A degree of freedom in layout about the porous partition wall, feeding pipe, communicating pipe and partition wall is remarkably restricted.